A producer faster than its consumer fills a queue, and what happens when the queue is full is a decision somebody makes — or a decision the infrastructure…
The replica was up, accepting connections and serving data from an hour ago. Seconds_Behind_Master reported zero, honestly, and was measuring the wrong thing.
94% coverage, and a suite that passes with the logic inverted. Coverage measures execution rather than verification, and there is a tool that measures the difference.
Full-fidelity tracing on a busy service is a considerable volume of data and a considerable bill, and almost all of it describes requests that were fine. Head-based sampling…